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The Cupola,


melt again and again,
even to twelve or thir-
teen times, but this
has now been demon-
strated to be a fallacy
(Seep. 779 ##^i o * i.)

To obtain a very
tough casting, such
as an hydraulic cy-
linder, wrought iron
turnings are some-
times mixed with the
pig in the cupola.

will now consider
how the moulder
forms his casting into
any desired shape.
To do this it is ne-
cessary in most cases
to make a wooden
pattern which shall
be the counterpart of
the casting required;
for several reasons we
shall see, however,
that the pattern will
not always be exactly
similar to the casting.
But more of this as
we advance.

The pattern is
impressed in sand
contained in two
moulding boxes, or
flasks, about half the
pattern in one box,
and half in the other;